1. Field of the Invention
This invention relates to a method and apparatus for suppressing the deposition of carbonaceous material in a regenerative coke oven battery and more particularly to a method and apparatus for both suppressing the deposition of carbonaceous material and removing deposits of carbonaceous material in a regenerative coke oven battery.
2. Description of the Prior Art
U.S. Pat. No. 2,306,678 entitled "Coke Oven Structure" is directed to a coke oven battery that includes an induction or recirculation duct connecting the vertical risers of flues on opposite sides of the coke oven chamber. In the illustrated embodiment the induction duct extends horizontally through the supporting mat of the coke oven battery beneath the regenerator walls. With this arrangement a portion of the products of combustion or waste gas is withdrawn through the vertical riser duct in the off flue and conveyed through the induction duct into the vertical riser duct of the on flue. The waste gas dilutes the rich fuel gas flowing upwardly through the vertical riser to the on flue. When a fuel gas of high calorific value or a fuel gas that includes constituents that tend to decompose at relatively low temperatures is used air may be introduced into the induction duct and admixed with the waste gas. The air is used to dilute the fuel gas in the on flue riser duct with oxygen and suppress the tendency to deposit carbon in the on flue riser duct. The amount of air introduced into the induction duct is controlled by the size of the orifice cap removably secured to the open end of a branch conduit connected to the induction duct. This arrangement supplies air at atmospheric pressure to the induction duct and is dependent on the suction effect caused by the flow of waste gas through the induction duct. Also, the air supplied to the induction duct is admixed with the waste gas and conveyed only through the vertical riser ducts of the on flue where it is admixed with the rich fuel gas flowing upwardly through the vertical riser to the on flue. With this arrangement the induction duct is open to the atmosphere and is dependent on the flow of waste gas through the induction duct to provide a suction effect for the air. If a substantial deposition of carbon occurs in the vertical risers or the vertical riser passageways clog, the opening in the induction duct for the inlet of air now becomes an opening for the escape of gas into the basement of the coke oven battery and could result in a hazardous and unsafe condition. Also, where rich gas, i.e. a gas containing the light oils (benzol, toluol and xylol), is used in a battery having recirculation or induction ducts, it is necessary to use abnormally large quantities of excess air during combustion. The excess air is utilized to remove the carbon deposited in the vertical risers associated with the off flues. The use of excess air results in inefficient combustion and frequently in underjet ovens overheats and damages the nozzles in the off flues.
In U.S. Pat. No. 3,222,260 there is disclosed apparatus for supplying air simultaneously to the high and low burners in the off flue and to further supply decarbonizing air during a portion of the on period to the low burners in the on flues while fuel gas is being supplied to the high burners and thereafter supply air to the high burners in the on flue while fuel gas is being supplied to the low burners in the same flue. With this arrangement there are two rich gas ports or burners in each flue and air is only supplied to the burners not being supplied with rich gas so that the rich gas is not diluted with the air as it flows upwardly through the vertical risers and the air only serves to remove the deposited carbonaceous material and does not suppress the deposition of carbonaceous material. British Pat. No. 1,341,271 also discloses apparatus to supply controlled amounts of air under pressure to the off flues for the removal of carbonaceous deposits.
There is a need to suppress the deposition of carbon in the vertical risers of the on flues and to reduce the amount of excess air employed during combustion. There is also a need for a method and apparatus to supply air to both of the vertical riser ducts in interconnected flues in controlled amounts to simultaneously and effectively decarbonize the vertical riser ducts of the off flues and suppress the deposition of carbon in the vertical riser ducts of the on flues.